Nasmyth Adaptive Optics System (NAOS) – Near-Infrared Imager and Spectrograph (CONICA)

Twinkling stars. An intriguing effect to admire during the night, commonly seen everywhere in the sky, but often more noticeable near the horizon. A beautiful effect with a simple explanation — small changes in the Earth's atmosphere distort the light waves from any astronomical object before they can reach our eyes — or an Earth-bound telescope!

So for astronomers, this phenomenon is a real nightmare, literally blurring out hours of observation over an entire night. And it’s not so simple to avoid — astronomers have to resort to a sophisticated technique called Adaptive Optics to compensate for this effect.

The Paranal Observatory’s NAOS+CONICA instrument, better known as NACO, is one of the best ground-based solutions to atmospheric turbulence. Thanks to its pioneering use of Adaptive Optics, NACO delivers images as sharp as if we were in space.

This instrument has two systems working together. First there is NAOS, or the Nasmyth Adaptive Optics System: an adaptive optics system equipped with visible and infrared sensors, which, due to a flexible mirror controlled by computer, counteracts the image distortion caused by atmospheric turbulence in real time.

The second part is CONICA, which is the infrared camera and spectrometer attached to NAOS. Together, they form the first adaptive optics system to have been installed on the Very Large Telescope (VLT).

NACO has been contributing to major discoveries in different fields of astronomy since 2001: exoplanets, the Galactic centre of the Milky Way, young stellar objects, Solar System bodies, etc.

NACO has observed planets orbiting other stars, providing the first-ever direct image of an exoplanet in 2004. By 2010, it had been able to directly follow the motion of an exoplanet as it moved from one side of the star Beta Pictoris to the other (eso1024). The instrument has also provided the first-ever spectrum of a directly observed exoplanet, allowing astronomers to study the planet’s atmosphere (eso1002).

Moreover, NACO was involved in one of the most important recent long-term astronomical research programmes. In a 16-year-long study, and after observing 28 stars, astronomers produced the most detailed view ever of the motions of the stars at the heart of our galaxy, the Milky Way — and providing evidence for the existence of a lurking supermassive black hole there.

During 2013 alone, 57 papers were produced by the scientific community with data obtained by NACO. NACO has now been moved from Unit Telescope 4 to Unit Telescope 1.

Science highlights with NACO

  • NACO observes an intriguing object near a young brown dwarf: the first direct image of an exoplanet (eso0428)
  • NACO observes Titan's atmosphere and surface (eso0505)
  • Fine images of Saturn and Io with VLT NACO (eso0204)
  • Exoplanet caught on the move (eso1024)
  • NACO tracks stars orbiting the supermassive black hole at the centre of the Milky Way (eso0846)
  • List of the scientific papers produced by NACO, via the ESO library’s TelBib database.

A raw image straight from NACO. This snapshot was obtained through the near-infrared K filter and, together with many other images, was used to create the iconic view of the centre of the Milky Way, reproduced at the top of this page. Many bright pixels pepper this single image; these are the hot pixels, which are typical of an infrared detector. They disappear several images obtained at slightly different positions are combined.


The authoritative technical specifications as offered for astronomical observations are available from the Science Operation page.

Site: Paranal
Telescope: Very Large Telescope, UT1
Focus: Nasmyth
Type: Adaptive-optics-assisted imaging, imaging polarimetry, coronography and spectroscopy
Wavelength coverage: 0.8–2.5 μm
Spatial resolution:
Spectral resolution: 400 in J, 500 or 1500 in H, 700 or 1400 in K, 700 or 1100 in L, 550 in SHK (1.3–2.6 µm)
First light date: October 2001 (eso0137)
Images taken with the instrument: Link
Images of the instrument: Link
Science goals:

Galactic centre
Young stellar objects
Solar System bodies



France: Office National d'Etudes et de Recherches Aérospatiales (ONERA), Paris;
Laboratoire d'Astrophysique de Grenoble (LAOG), Grenoble; Observatoire de Paris, Paris

Germany: Max-Planck-Institut für Astronomie (MPIA), Heidelberg;
Max-Planck-Institut für extraterrestrische Physik (MPE), Garching